New Solution For Wastewater Treatment In Plating Industry: High Performance Forward Osmosis Membrane From Hydrophilic Material

Recent research by scientists from the Institute of Science and Technology for Energy and Environment, Vietnam Academy of Science and Technology, has successfully developed a high-performance forward osmosis (FO) thin membrane that helps remove heavy metals from plating wastewater. This is an important step forward in the application of environmentally friendly membrane technology to solve the problem of industrial water pollution in Vietnam.

Currently, the electroplating industry, an important field in mechanical, electronic and automobile manufacturing, is becoming a serious source of water pollution. During the electroplating process, wastewater contains large amounts of toxic heavy metals such as arsenic, lead, nickel and chemicals such as cyanide and sulfate. Only a small part of these substances is treated, the rest is discharged into the environment, causing long-term harm to human health and the ecosystem.

Many treatment technologies have been applied such as chemical precipitation, ion exchange, adsorption or nanofiltration, but the limitations of these methods are high cost, sludge generation or low efficiency in complex wastewater conditions. Meanwhile, FO technology has emerged as a promising solution thanks to its ability to save energy, less fouling and is especially suitable for removing heavy metals. However, one of the major obstacles of FO is the low permeation flow due to the phenomenon of concentration polarization. From this challenge, MSc. Le Xuan Thanh Thao and the research team have successfully implemented the topic: "Fabrication of high-performance forward osmosis thin membranes and applications in removing heavy metals from plating wastewater" (Code: VAST07.02/23-24), with the goal of successfully developing a new type of FO membrane with higher efficiency thanks to the integration of hydrophilic dextran material, providing a more feasible solution in the treatment of wastewater from the electroplating industry today.

Optimizing membrane structure - increasing separation efficiency
The research team showed that dextran material - a natural polysaccharide with high hydrophilicity when added to the polyethersulfone (PES) base layer significantly increased the porosity and wettability of the membrane, the water contact angle decreased, the pore density increased, and the cross-sectional layer structure became more porous. The changes were clearly demonstrated through scanning electron microscopy (SEM).

This improvement has directly helped the FO membrane overcome the internal concentration polarization effect, one of the biggest limitations of traditional membrane systems, which reduces the effective osmotic pressure and makes the water flow through the membrane much lower than the theoretical one. The base layer containing 5% dextran helps double the water permeation rate compared to commercial thin-film composite (TFC) membranes under the same testing conditions, while still maintaining the ability to effectively block salts and heavy metal ions, achieving a removal efficiency of over 97% for metals such as As, Pb, Ni, etc.

From the success in the laboratory, the group has deployed to evaluate the possibility of practical application through simulation experiments of wastewater containing heavy metals from the plating industry. MSc. Le Xuan Thanh Thao said: In the forward osmosis process FO, the feed solution (FS) with low osmotic pressure and the diluent solution (DS) with high osmotic pressure are separated by a semi-permeable membrane. Factors affecting the membrane performance such as pH, concentration of feed solution and diluent solution mentioned above have been thoroughly analyzed, contributing to clarifying the operating mechanism of the membrane under different practical conditions.

Unlike many previous studies that focused mainly on membrane structure, scientists have deeply exploited the relationship between structure - properties - performance, providing a systematic and highly practical approach for water treatment applications. Compared with recent studies using nanomaterials such as graphene oxide or zeolite to improve filter membranes, the method using dextran is not only biologically safe, low cost but also suitable for the technological conditions of small and medium-sized production facilities in Vietnam.

From the research results, the group has built a high-performance FO membrane manufacturing process and a complete membrane filter model, ready for application transfer. At the same time, the research results have been published in international journals in the SCIE category (Q2) and domestic scientific journals. Two articles have clearly shown the potential for practical application of this technology. In particular, the international article published in the Chemical Engineering Research and Design journal has demonstrated that the addition of dextran helps double the water flow compared to commercial TFC membranes, while maintaining stable filtration efficiency. The second article focuses on the application of removing arsenic, a common carcinogen in plating wastewater and groundwater, thereby showing that the TFC-Dex membrane is not only technically effective but also suitable for urgent environmental issues in Vietnam.

According to MSc. Le Xuan Thanh Thao: The research focuses on improving the properties of materials with the higher goal of creating a feasible solution suitable for the actual conditions in Vietnam. “We want to develop a membrane that is not only effective in the laboratory but can also be applied in small and medium-sized production, where the requirements of cost, stability and simple operation are very important,” added MSc. Thao.

She also said: Choosing biological materials such as dextran helps improve membrane performance, ensuring safety, environmental friendliness and the ability to produce on a large scale. The most important thing is that the technology must approach both technical and economic requirements. If it stops at the ideal model, the technology will be very difficult to put into practice.

Compared with current filtration technologies, especially the reverse osmosis (RO) system which consumes a lot of energy, the FO membrane technology in this study offers a clear advantage in energy saving and can be flexibly integrated in both FO and RO systems. With almost absolute metal ion removal efficiency, durable membrane structure and simple manufacturing process, the new technology is not only suitable for wastewater treatment in the electroplating industry but can also expand the application scale in other fields such as water reuse, industrial wastewater treatment or pre-treatment for fine filtration systems. The initial success of scientists has opened up a new approach in environmental treatment in a cost-effective and sustainable direction.